Frequency multiplication system



Dec. 24, 1935. J. PLEBANSKI FREQUENCY MUL TIPLICATION SYSTEM Filed Sept.12, 1934 5 Sheets-Sheet 1 INVENTOR ATTORNEY Dec. 24, 1935.

J. PLEBANSKI FREQUENCY MULTIPLICATION SYSTEM Filed Sept. 12, 1934 3Sheets-Sheet 2 INVENTOR JOSE? PLEBANSM BY %f/%hx ATTORNEY Dec. 24, 1935.J. PLEBANSKI 2,025,610

FREQUENCY MULTIPLICATION SYSTEM Filed Sept. 12, 1954 r L 3 Sheets-$heet5 INVENTOR IOSEF PLEBAN5K\ ATTORNEY Patented Dec. 24, 1935 UNITED STATESTDAENT OFFICE FREQUENCY MULTIPLICATION SYSTEM Application September 12,1934, Serial No. 743,698 In Poland July 10, 1931 12 Claims.

My invention relates to improvements in radio systems and method ofoperation, and has for its main object to provide a new method and meansfor frequency multiplication.

In many cases, it is desirable to operate with a relatively lowfrequency in one part of a radio system, such as a transmitter orreceiver and to use relatively higher frequencies in other parts of thesystem. This necessitates the provision of frequency multiplying meansbetween the different portions of the system. An example of this occursin single side-band transmission systems. The advantages of singleside-band transmission with or without carrier suppression are wellknown. A substantial saving in transmitting power obtained through thesuppression of the other side-band with or without the carrier frequencyis elfected.

A condition, however, encountered in transmission systems of this typeis the fact that the suppression of the other side-band can beeffectively carried out with low frequencies only, such as of the orderof about twenty kilocycles for which filters with a sharp cut-oifcharacteristic can be constructed. When starting with a low carrierfrequency of the above order, it is necessary to increase the frequencyto a higher carrier frequency by means of a frequency multiplicationarrangement. In using the commonly known frequency multiplicationsystems such for example as one involving a non-linear characteristicvacuum tube for distorting the wave shape from which the desired highfrequency is segregated by suitable filter means, great difiiculties areencountered due to undesired cross modulation produced between theside-band frequencies of the modulated carrier. This results insubstantial distortion and interference of the signals beingtransmitted.

Accordingly, an object of my invention is to provide a new method of andmeans for multiplying a given, and particularly a modulated, frequencywithout inducing interaction or cross modulation between the side-bandfrequencies.

Another object of the invention consists in providing an improved andsimplified system for single side-band transmission with or withoutcarrier frequency suppression and which is substantially free fromdistortion and similar objectionable interference inherent in systems ofsimilar nature.

A further object of the invention consists in providing a new method oftransmitting and reconstructing a carrier frequency for single sidebandtransmission systems to substantially reduce,

fading and similar objectionable phenomena. The invention has otherobjects in view which will appear hereinafter in a detailed descriptionthereof in connection with the accompanying drawings in which:

Figures 1 and 2 are schematic diagrams illustrating the novel method andprinciple of frequency multiplication embodied in the invention. Figure3 shows one practical arrangement for carrying out the invention.

Figure 4 illustrates the response characteristic of a filter adapted forsingle side-band systems.

Figure 5 illustrates a modified circuit arrangement embodying the novelmethod of frequency multiplication as applied to single side-bandtransmission.

Figure 6 illustrates a modification of the circuit shown in Figures 3and 5.

Figure 7 is a circuit diagram for receiving a single side-bandtransmission with auxiliary side frequencies for reconstructing thecarrier frequency;

Figures 7a and 7b illustrate response characteristics explanatory of theoperation of the circuit of Figure 7 and Figure 8 illustrates a furthermodification of the system shown in Figure 3.

The novel method of frequency multiplication according to my inventioninvolves the use n is the carrier frequency in a radio transmission A1sin W1t+A2 sin W2t= cos (W1-- W2) t in which w1= 271'fh and w2=21rfs.

V. manner, a modulated frequency 21% is obtained which in turn iscombined by means of a further In this manner the frequency is istransformed in the modulators M1 and M1 into its combination frequenciesn+1, and fhfs of which the latter. is segregated by suitable resonantmeans in the modulator M1 and the former is segregated in the'modulatorM1. The thus obtained combination frequencies fh-i-fs and fh-fs arethen'in turn combined as shown in the second modulator M2 thus yieldinga combination frequency ,fs+fh+fsfn=2fs; that is, double the original orcarrier frequency f5. The double frequency 2fs thus obtained is thencombined with the auxiliary frequency is by means of a pair of furthermodulators M3 and M3 in a similar manner as previously described toproduce side frequencies 2fs+fn and 2fsfn yielding a further combinationfrequency equal to 4fs produced by the modulator M4. In this manner, aswill be understood from Fig. 1, any harmonic of the series 2" .fs of theoriginal or signalling frequency may be obtained and applied to autilization circuit such as an amplifier transmission line or wirelessantenna.

In Figure 2 I have shown a schematic arrangement similar to Figure 1 forthe multiplication of a modulated carrier fs specifically used in asingleside-band transmission system for suppressing the side-band bymeans of a filter in the low frequency stage. For this purpose I haveshown modulators m, ml, m2, m3, m4 mn, illustrated by cross-hatchedrectangles carrying the modulated frequency currents, while the over theline I to the modulator m-which is furthermore supplied with thefrequency is. In

this manner a modulated carrier is obtained which is combined in afurther modulator m1 with the auxiliary frequency in, thus yieldingmodulated intermediary frequencies fs-fh. and fs+fh. At this stage, oneof the side-bands 'may be suppressed, such as by means of a sharpcut-off filter having a characteristic as shown "in Figure 4. At thesame time, the carrier may also be suppressed by the proper design ofthe filter to encompass both one side-band and the carrier frequency asis understood. The modulating intermediary frequency fs-fh is thencombined by means of a further modulator with an unmodulatedintermediary frequency fs+.fh supplied from the modulator M1 as shown.In this modulator m3 with the auxiliary frequency In yielding a secondintermediary modulated frequency 2fs--fh, which latter is in its turncombined in a further modulator 1m with the unmodulated, obtainedwhichmay be combined in a common output for suppression of the carrier or, ifthe carrier has been previously suppressed.

for restoration of the carrier in the common. out:

supplied'from a suitable source IE to the power amplifier 3 by means ofa high frequency transformer 4. The modulation shown is the well knownanode current or Heising modulation. For this purpose the output of theamplifier tube is directly connected to the anode of the power amplifiertube 3 whereby the high frequency currents in the output of the tube aremodulated in accordance with the low frequency or modulating currents.From the output of tube 3, the modulated high frequency s is applied tothe input of a modulator amplifier or frequency converter tube 6.through transformer 5. In addition currents of the auxiliary frequencyin produced by a generator IT are applied to the modulator amplifiertube 6 as shown, resulting in the production of combination intermediaryfrequencies in the output of tube 6 of which the component fwfh issegregated by means of a filter F which may have a characteristic asshown in Figure 4 and may be designed to simultaneously suppress thecarrier frequency as pointed out before. The thus obtained modulatedfirst intermediary frequency is then applied to a further modulatingtube 1 for combination with the unmodulated intermediary frequency fH-fnsupplied from the tube 9 of the unmodulated multiplier system to theanode of the tube! in Heising modulation arrangement.

The unmodulated intermediary frequencies are produced by means of a pairof modulator-converter tubes 8 and I2 with input circuits supplied withthe carrier frequency is through transformers l0 and II, respectively,and with the frequency In directly applied to the input circuits oftube-s 8 and 12 as shown. In this manner combination frequencies fs+fnand fs-fh are produced'in the output circuits of tubes '8 and I2,respectively, of which the former is segregated in the output of tube 8and the latter is segregated in the output of tube I2 by suitableresonant means. The single intermediaries thus obtained are then appliedthrough transformers l4 and [5, respectively, to the input of a pair offurther tubes 9 and [3 whose anodes are connected for mutual modulationproducing an unmodulated frequency 2fs in their common output circuitsconnected throughtransformers I8 and IS with the anode circuits of tubes9 and I3, respectively. The modulated and unmodulated double frequency2fs thus obtained may be further mutually combined with the: auxiliaryfrequency in in a similar manner to produce any desired mul- I tipleaccording'to the series 2% as explained in connection with the schematicshowing in Fig- 6 ure 2. 20 and 2| are coupling coils connecting theoutput of tubes 1 and 9 to a common output circuit carrying the, doublecarrier frequency 2h Figure 5 shows a modification of the circuit ofFig. 3 using a return or reflex arrangement from a stage carrying amultiplied frequency to the input circuit of the initial frequencycurrent resulting. in a great simplification of the circuit.

'As shown, an audio-transformer l controls the speech amplifying tube 2serving to modulate the power amplifier 3 controlled. by carrierfrequency is. The modulated carrier is applied to the input of amodulator amplifier 6 which is also controlled by the auxiliaryfrequency in, thus yielding a one side-band modulated intermediaryfrequency fs-fh by the further use of a suitable filter in a mannersimilar to that described in connection with Fig. 3. This latter isapplied to the input of a further modulator tube 1 together with anon-modulated intermediary frequency fs+fh supplied through atransformer 32 from the unmodulated carrier multiplication system. Inthis manner a modulated double carrier frequency 21% is obtained in theoutput of the tube 1 which is applied to the input of a furthermodulator amplifier tube 24 together with the auxiliary fa resulting ina combination frequency 2fsfh in the output of tube 24, which latter isin turn applied to the input of modulator amplifier 35 together with anon-modulated second intermediary frequency Zfs-I-fh supplied throughtransformer 29 from the unmodulated carrier system. In this manner, amodulated four-fold carrier 4fs is secured in the output of tube 35which by means of a transformer 36 may be combined with thenon-modulated carrier 4J5 as shown supplied by the transformer 33 eitherfor suppressing or restoring the carrier.

The non-modulated multiplication system comprises a first modulator tube26 having its input controlled by both carrier frequency f5 andauxiliary frequency fh, thus yielding two combination frequencies fs-fhand fs+fh which are both segregated by means of resonant circuitsinserted in the output circuit of the tube and in turn combined in theinput of a modulator tube 37 through coupling transformers 36 and 3!respectively. The resonant circuit carrying the frequency fs+fh isfurthermore coupled to the input of the tube 1 through transformer 32 asdescribed before, to combine with the signal modulated intermediary fsfafor securing a modulated carrier 2fs in the output of the tube 1. Bycombination of the intermediary frequency fsh and ,fs-l-J'h by tube 31,a non-modulated double carrier frequency is secured in the output of thetube 31 which is returned or refiexed through transformers 34 and 35- tothe input of the first modulator tube thus combining with the auxiliaryfrequency ft and producing further intermediate frequencies 2fs-fh and2fs+fh in the output circuit of the tube 26, which are segregated bymeans of suitableresonant circuits as shown and applied throughtransformers 21' and 28, respectively, to the input'of a modulator tube38 for combination to yield a fourfold unmodulated carrier 4J5 in itsoutput circuit which as described may be combined with the modulatedfour-fold carrier as shown. The intermediate frequency 2fs+fh isfurthermore applied through transformer 29 to the: input of the tube 35for combination with the signal modulated intermediary frequency 2fsfhas described hereinbefo-re. Otherwise the circuit and. its operation issimilar to that described in connection with Figure 3.

Figure 6 shows a circuit arrangement similar to Figure 5 formultiplication of the initial frequency to its sixteenth harmonic. Inplace of vacuum tube modulators for changing of the frequency, I haveshown rectifiers, such as dry rectifiers or crystal rectifiers or thelike arranged in a well known bridge circuit. In this manner the entirecircuit is greatly simplified and both the installation and maintenancecosts greatly reduced. As is obvious, the generators I6 and I! for thecarrier frequency and the auxiliary frequency in this case must bedesigned for increased power or provided with suitable amplifiers. Thecircuit according to Figure 6 also utilizes the reurn or reflexprinciple as will be described in detail.

This circuit also substantially comprises a first system for multiplyingthe signal modulated carrier and a second system for multiplying theunmodulated or pure carrier and mutual circuit connections for combiningmodulated intermediary frequencies with unmodulated intermediaryfrequencies in a manner similar as described before to secure a finalmultipled output frequencyof a desired order free from distortion and.similar eifects inherent in systems heretofore known in the art.

Referring to the circuit arrangement of Figure 6, I have shown an inputtransformer I for applying the modulating, such as audio frequencycurrents supplied from a microphone or the like to a first modulatingcircuit 40 including a rectifier arrangement 4| comprising fourrectifier elements such as dry or contact rectifiers connected in thewell-known bridge circuit as shown. The circuit 4!) furthermore issupplied with carrier frequency currents applied through transformer 45from a circuit including the carrier frequency generator I6. In thismanner a modulated carrier Mm) is obtained and applied to anintermediate or filter circuit 42 of known design. From the circuit 42the modulated carrier is applied to a further modulating circuit 43including a rectifier arrangement 44 and supplied with auxiliaryfrequency currents supplied through transformer 10 from a circuitincluding the auxiliary frequency generator l1. manner a firstintermediary signal modulated frequency is obtained of which oneside-band (such as fs-l-fh in the example shown) with or without thecarrier may be suppressed such as by means of a suitable filter :35 asshown. This frequency is then applied to a modulating circuit 41including a rectifier arrangement 48 and also carrying currents of theunmodulated intermediary frequency is-l-fh supplied from the unmodulated multiplication system through transformer 8%. In this mannera. multiple modulated carrier frequency 2fs(m) is produced in thecircuit 4-"! and its associate filter circuit 49. The frequency 2mm) isthen applied to the modulation circuit 59 including a rectifyingarrangement 5| and also carrying currents of the auxiliary frequency inapplied through transformer 1| connected in the auxiliary frequencycircuit of the generator ll.

mediate resonant circuit 53 is applied to a further modulation circuit54 including a'rectifying arrangement 55 and also carrying currents ofthesecond unmodulated intermediary frequency I 2fs+fh supplied from theunmodulated multiply- The result- In this The resulting combinationfrequency 2fs-fh(m) after passing through inter- (iii ' iliary generatorl1.

idiary circuit 59 is then combined in circuit 60 includingrectifying'arrangement 6| with a nonmodulated intermediary 4f8+fnsupplied from the unmodulated multiplier through transformer 8| asshown. In this manner a modulated frequency 8fs(m) is obtained, whichafterpassing through intermediary circuit 62 is combined in a furthermodulation circuit 63 including a rectifying arrangement 64 with theauxiliary frequency in applied to the circuit through transformer 13from the circuit ofthe auxiliary generator IT. The resulting modulatedintermediary frequency 8js-fh(m) after passing through intermediatecircuit 65 is then combined in the modulation circuit 66 includingrectifying arrangement Bl with the unmodulated intermediary 8fs+fhsupplied from the unmodulated multiplier through transformer 95. Fromthis there results a final'modulated carrier 16mm) applied to the I A Asin W11 A2 sin Wat 2 intermediate circuit 68 and which may be comlatedfrequency 16f5 in the intermediate circuit I00 which may be combinedwith the signal modulated frequency 1675 as described.

In the arrangements according to Figures 5, 6

and 8, the desired beat or combination frequencies are segregated bymeans of resonant circuits, It is understood that any other segregatingmeans or filters such as piezo crystals or the like with or withoutassociated amplifiers may be provided for this purpose. It isfurthermore understood that the reflex arrangement may be employedrepeatedly, resulting in a further simplification of the circuitarrangement as is obvious.

An arrangement as shown in Figure 6 using rectifiers such as dryrectifiers, diodes, etc., has the great advantage that the modulation ofthe frequency ,fs by the frequency in or its harmonics 211.13 is linear;that is, the modulation conforms a general to the formula:

When vacuum tubes are used for the transposing of the frequencies withnon-linear characteristics, the modulation conforms to the formula:

pression or restoration of the carrier as described before in a commonoutput circuit to be connected to terminals a and b.

The unmodulated carrier multiplier is comprised of a first modulatorcircuit 18' including a rectifier arrangement 83 and supplied with thecarrier frequency is through transformer 18 and with the auxiliaryfrequency in through transformer T4. The resulting combinationfrequencies ,fs+fh and ,fsfn are segregated by means of intermediarycircuits coupled through transformers 83 and 82, respectively, andcombined in a modulating circuit 81 including a rectifying arrangement88, thus yielding a frequency 2js in the associated intermediate circuit90. The frequency 2fs is then applied from the circuit 90 to amodulating circuit 90 including a rectifying arrangement 82 and alsocarrying currents of the auxiliary frequency is supplied throughtransformer 15 connected in the circuit of the aux- V The resultingcombination frequencies 2fs+fh and 2,fsfh are segregated by means ofintermediate resonant circuits. coupled through transformers 92 and 96,respectively, and

' then combined in a modulation circuit I02 including a rectifyingarrangement I03.

The resulting frequency 4fs produced in the circuit I02 is returned orfed back in a reflex arrangement to the first modulation circuit 18'through transformers I04 and I05 where it is combined, with theauxiliary frequency In, yielding intermediate frequencies 4fs+fh and4fsfh which are segregated by means of resonant intermediate circuitscoupled to the circuit 18" through transof intermediate circuits coupledto the transformers 94 and 93 and in their turn combined in 'amodulation circuit H19 including a rectifying From the last two membersof the formula, it is seen that frequencies 2w1t and 2wzt are producedand in addition there will be higher harmonies of these frequencieswhich may cause interference and distortion of the signals beingtransmitted. The circuit according to Figure 6 is free from thisdisadvantage as already pointed out.

The arrangements according to Figures 2, 3, 5 and 6 can be furthersimplified where it is required to suppress one side-band and thecarrier frequency. A simplified arrangement of this is shown by Figure 8which merely differs from Figure 2 by the employment of harmonicfrequencies of the auxiliary generator I1 such as the harmonic 2fh usedfor heating with the modulated multiplied freqency 21% as shown,otherwise the circuit is similar in design and function to previouscircuits as will be understood.

Referring to Figure 7, this shows a receiving system especially adaptedtherewith in connection with the invention and for communication with asingle side-band and elimination of the carrier frequency. As iswellknown in systems of this type, means must be provided at the receiverfor restoring the carrier necessary for reproducing the originalsignals.

In order to restore the carrier at the receiver 'means known in the art.In addition to this sin- 1 'gle side-band, two further side-bands orside frequencies are produced, for instance, by modulation according toa single not outside of the regular modulation band such as of 6000cycles in the above example. Such pilot bands or frequencies may easilybe obtained by modulating the carrier in the final stage with afrequency of 6000 cycles and combining it with the m0dulated frequencyin such a manner that the carrier itself is suppressed; Any suitablemeans known in the art may be provided for this purpose, such as abalanced modulator and the like. Thus, two pilot frequencies orside-bands are obtained produced by the oscillations of 6000 cycles anda single modulated side-band produced by the signalling modulation andcomprising 30 to 4000 cycles.

At the receiver the modulated side-band of 30 to 4000 cycles is receivedby a suitable filter F2 having a response characteristic as shown inFigure 7 b and applied either directly or through any suitable frequencychanging means to the detector tube II6 for reception by a translatingmeans such as loud speaker H with interposed amplifier well known in theart. The side frequencies produced by the oscillations of 6000 cyclesare passed through filter F1 having a response characteristic as shownin Figure 7a, and applied to a frequency doubling tube III or any otherarrangement for doubling the frequency. In this manner the carrier waveof double frequency is restored in accordance with the equa tion:

This pilot frequency is then utilized for controlling an oscillator H2having a frequency of Z =WL The frequency of the oscillator is appliedto the detector tube I I6, thus restoring the original carrier frequencyfor de-modulation and reception of the signal. In place of a singlepilot frequency, such as 6000 cycles as in the example given, it isunderstood that a band of pilot frequencies may be provided andtransmitted.

The above method of transmitting the carrier frequencies by means of itsside-bands involves the great advantage of reducing the effects producedby fading, especially so-called selective fadings. The arrangementaccording to Fig. '7 may be furthermore modified by doubling the singlemodulated side-band passed through the filter F2 by means of a frequencydoubling arrangement such as of the type described hereinbefore andshown for instance by Fig. 3, and then to combine the doubled carrierfrequency produced by the frequency doubling tube I I I. In the lattercase an additional auxiliary oscillator will be necessary as shown atfh. I have furthermore shown at I II! an input amplifier and an antennaI I3 with ground connection H4.

While the invention has been described with specific reference to theshowing of the drawings, I desire it to be understood that variousmodifications may be made and that no limitations upon the invention areintended short of its broad and underlying spirit as expressed in theappended claims.

I claim:

1. The method of frequency multiplication consisting in combining afundamental frequency wave with an auxiliary frequency wave to derivesum and difference combination frequency waves, combining saidcombination frequency waves to derive a further combination frequencywave therefrom equal to the second harmonic of said fundamentalfrequency Wave, combining said second harmonic frequency wave with saidauxiliary frequency wave to derive secondary sum and differencecombination frequency waves therefrom, and combining said secondarycombination frequency waves to produce a further combination frequencywave equal to four times the frequency of said fundamental frequencywave and successively continuing the process until obtaining a finaldesired harmonic frequency wave of the order 2 of the fundamentalfrequency.

2. The method of frequency multiplication consisting in combining afundamental signal modulated carrier frequency wave with an auxiliaryfrequency Wave to derive therefrom sum and difference combinationfrequency waves, producing similar combination sum and differencefrequency waves from an umnodulated fundamental carrier frequency waveand said auxiliary frequency wave, and combining a combination frequencywave derived from the modulated carrier with a combination frequencywave derived from the unmodulated carrier to produce a modulated secondharmonic of said carrier frequency wave.

3. The method of frequency multiplication consisting in beating afundamental frequency signal modulated wave with an auxiliary frequencywave to derive therefrom sum and difference combination frequency waves,producing similar sum and difference combination frequency waves bybeating an unmodulated fundamental wave of the same frequency as saidfundamental signal modulated wave together with said auxiliary frequencywave, combining a combination frequency wave derived from said modulatedfundamental frequency wave with a com,- bination frequency wave derivedfrom said unmodulated fundamental frequency to produce a modulatedsecond harmonic of said fundamental frequency wave, producing a secondharmonic of said unmodulated fundamental frequency wave, combining saidsecond harmonic modulated fundamental frequency wave with said auxiliaryfrequency wave to derive secondary sum and difference combinationfrequency waves therefrom, producing similar secondary combinationfrequency waves by beating together said second harmonic unmodulatedcarrier frequency wave and said auxiliary frequency wave and combining asecondary combination frequency wave derived from said modulated secondharmonic wave with a combination frequency derived from said unmodulatedsecond harmonic wave to produce therefrom a modulated fourth harmonic ofsaid fundamental frequency wave and continuing the process by producingfurther successive harmonies of said unmodulated fundamental frequencyWave of like order supplied by said first said auxiliary frequency waveto derive combination frequency waves of the respective orders andcombining said fourth harmonic modulated carrier wave with saidauxiliary frequency wavei and beating a resultant combination frequencywave with a corresponding combination frequency wave of like harmonicorder of the unmodulated fundamental frequency wave to produce an 8thharmonic'modulated wave of said fundamental frequency wave andanalogously continuing the process until obtaining a desired modulatedharmonic wave of the 2 th order of said fundamental frequency wave.

4. The method of frequency multiplication as claimed in claim 3 in whichsaid further harmonies of said unmodulated carrier frequency wave areproduced by combining combination frequency waves derived therefrom byheating with said auxiliary frequency wave.

5. In a method of frequency multiplication as claimed in claim 3including suppressing the carrier frequency component of the initialfundamental modulated carrier frequency wave and re- 7 introducingacarrier in the final stageobtained from multiplication of theunmodulated initial carrier wave frequency wave having the frequencynecessary for said re-introduction to produce an output signal with acarrier component.

6. The method of frequency multiplication as claimed in claim 3including suppressing one sideband of the initial fundamental modulatedcarrier frequency wave and suppressing the carrier frequency componentin the final stage by combination with the multiplied unmodulatedcarrierwave having the same frequency .as said carrier frequency.

'7. A frequency changing system comprising a source for producing afundamental carrier frequency wave, a further source for producing anauxiliary frequency wave, means for combining said frequency waves toderive sum and differcombination frequency waves, further means forbeating said combination frequency waves to derive a second harmonic ofsaid fundamental frequency wave, and means for beating said harmonicfrequency wave with said auxi1- iary frequency wave and beatingresultant combination frequency waves to produce the fourth harmonicwave of the fundamental frequency wave and continuing the process ofproducing harmonic waves by beating with said auxiliary frequency waveand beating together resultant combination frequency waves substantiallyas described until obtaining a final desired harmonic wave of the 2 thorder of the said fundamental frequency wave.

8. A frequency changing system comprising a source for producing afundamental carrier frequencywave, a further source for producing anauxiliary frequency wave, a first mixing circuit for combining saidcarrier frequency wave and said auxiliary frequency wave to derive sumand difference combination frequency waves, a sec' ond mixing circuitfor combining said combination frequency waves to derive a second harmonic beat frequency wave of said fundamental, a third mixing circuitfor beating said second harmonic frequency wave with said auxiliaryfrequency wave to derive secondary combination frequency waves, a fourthmixing circuit for combining said secondary combination frequency wavesto derive therefrom a fourth harmonic .wave of said fundamental, andfurther mixing circuits for producing higher harmonics of saidfundamental frequency according to the series 2 until obtaining adesired fourth final harmonic frequency'wave of desired order.

9. In a frequency changing system as claimed in claim 7, including meansfor feeding currents from a circuit carrying a wave. of higher harmonicorder to a circuit carrying a wave of lower harmonic order for producingcombination frequencies between said currents and said auxiliaryfrequency wave in the mixing circuit for said lower harmonic frequencywave.

.10. A frequency changing system comprising a source for producing afundamental carrier frequency wave; means for modulating said carrierfrequency in accordance with signal variations; a source for producingan auxiliary frequency wave; means for deriving an unmodulated componentof said carrier frequency wave; a first multiplication system forincreasing said unmodulated carrier component comprising firstheterodyning means for combining one unmodulated carrier with saidauxiliary frequency wave to derive a combination frequency wave furtherheterodyning means for combining said combination frequency wave toderive a second harmonic carrier frequency wave, further heterodyningmeans for combining said second harmonic carrier frequency wave withsaid auxiliary frequency wave for producing combination frequency wave,means for heterodyning said latter combination frequency wave to producea fourth harmonic of said carrier frequency wave, and means foralternately heterodyning harmonic frequency wave of said carrier withsaid auxiliary frequency wave and for mutually heterodyning theresultant combination frequency wave to produce a final desired harmonicof the 2 order of said unmodulated carrier frequency wave; and a secondmultiplication system for increasing said modulated carrier componentcom-.

prising first mixing means for combining the modulated fundamentalcarrier frequency wave with said auxiliary frequency wave to derivecombination frequency wave; further mixing means for combining one ofthe latter combination frequency wave with a combination frequency waveof like order of said unmodulated carrier component supplied by saidfirst multiplication system to produce amodulated second harmoniccarrier frequency wave; additional mixing means for combining saidmodulated second harmonic carrier frequency wave with said auxiliaryfrequency wave to derive combination frequency Wave therefrom; furthermixing means for combining one of said latter combination frequency wavewith a corresponding combination frequency wave of like order suppliedby said first multiplication system for producing a modulated fourthharmonic carrier frequency wave; and additional means for alternatelyheterodyning modulated harmonics of said carrier frequency Wave withsaid auxiliary frequency wave and heterodyning resultant combinationfrequency wave of the modulated carrier frequency wave with acorresponding combination frequency wave of like order of theunmodulated carrier frequency wave supplied by said first multiplicationsystem to secure a final modulated carrier of the 2 order of thefundamental carrier frequency wave.

11. A frequency changing system as described in claim 10 for singleside-band transmission I

